1. Field of the Invention
The present invention relates to systems and methods for diffusing gas into a liquid by creating and maintaining conditions that create a mixture of the liquid and bubbles of the gas. In some non-limiting implementations, the described systems and methods also include adding bacteria and/or bacterial nutrients to the liquid.
2. Background and Related Art
Aeration plays important roles in many industries where process efficiency depends on a concentration of oxygen in the processed liquid (i.e., brewing, environmental services, waste-water treatment, farming, fishery, and/or mineral processing). Some traditional methods of creating conditions for aeration include the use of simple aerated tanks, spray towers, bubble-tray columns, and packed columns to create a gas-liquid interface. Often traditional aeration technology uses counter-current flow methods and multiple stages that allow the gas to be absorbed in the desired liquid. While these traditional methods and associated apparatus do achieve aeration, they can be inefficient, requiring long processing times and, hence, large equipment volumes. The inefficiency associated with some traditional approaches arises largely from the relatively low gas-liquid interfacial area to volumes provided by the equipment.
It has been suggested that improved aeration performance may be achieved through the use of an air-sparged hydrocyclone similar to designs used in the mineral processing industry for separation of solid particles from an aqueous suspension. Often such air-sparged hydrocyclones are based on the concept of passing bubbles of air through a suspension of solid particles so that hydrophobic particles attach to air bubbles and form a cohesive froth that may be removed from the separation vessel. In other words, the design of such air-sparged hydrocyclones is often concerned with the creation of gas-liquid contact conditions that are favorable for efficient particle to bubble interaction and separation with mass transfer.
In addition, various methods of, and apparatus for, removing volatile content (“VCs”) from water and other liquids have been known and used in the prior art for a number of years. One of the traditional approaches, generally referred to as “air stripping”, removes VCs from a contaminated liquid by passing a stream of clean air or other gas through the water or other liquid so that VCs transfer from the liquid to the gas and may be removed from the system with the exiting gas. The operating parameters of some such air stripping devices are selected to optimize the overall efficiency of both mass transfer between gas dissolved in the liquid phase and gas passing through the liquid. Additionally, the flow rate of liquid in some such devices needs to be set to produce centrifugal force fields with radial accelerations between 400 Gs and about 1500 Gs, compared to accelerations of about 70 Gs used for particle separation.
In general, some methods of air-stripping, dynamically mix gas bubbles with liquid (thereby rapidly replenishing the supply of molecules of the transferring component in immediate proximity to the gas-liquid interface and minimizing mass diffusion limitations on transfer rate), optimize the contact time between bubbles and liquid (thereby allowing material transfer to reach or closely approach equilibrium), and cleanly separate post-contact gas and liquid streams (thereby minimizing regressive transfer). In many such methods, the objective is to maximize gas velocity flowing through the liquid and diverting both phases (liquid and gas) at the apparatus exit. If a large volume of gas passes through the unit of liquid, then mass transfer of gas dissolved in liquid into passing gas is maximized, increasing overall gas stripping efficiency. Accordingly, some such devices work in the regime of very high Gs, promoting movement of gas from liquid to gas—but not in reverse.
In addition to the aforementioned methods for aerating, removing contaminants from, and otherwise treating liquids, some conventional methods for treating contaminated liquids (e.g., water comprising hydrocarbons from an oil spill) involve applying synthetic, petroleum-based chemical surfactants to the liquid. While such surfactants may act to emulsify contaminants in the liquid, and thereby allow such contaminants to mix and disperse, such surfactants are often toxic to humans, animals, and the environment and can even be non-biodegradable.
Thus, while techniques currently exist that are used to aerate liquids and to treat liquids (such as contaminated water), challenges still exist, including those discussed above. Accordingly, it would be an improvement in the art to augment or even replace current techniques with other techniques.